Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$62.79	12.189%	$70.4435	$70.44	$70.45	$70.40
Purchase #2	$72.26	3.628%	$74.8816	$74.88	$74.90	$74.90
Purchase #3	$26.84	5.769%	$28.3884	$28.39	$28.40	$28.40
Purchase #4	$168.81	3.776%	$175.1843	$175.18	$175.20	$175.20
Purchase #5	$67.52	8.309%	$73.1302	$73.13	$73.15	$73.10
Purchase #6	$64.33	13.302%	$72.8872	$72.89	$72.90	$72.90
Purchase #7	$165.92	3.210%	$171.246	$171.25	$171.25	$171.20
7 purchase totals =	$628.47		$666.1612	$666.16	$666.25	$666.10